1. Field of the Invention
The present invention relates generally to entertainment and architectural lighting. Specifically, the invention is a device for use in a lighting fixture and or light projectors that collects light and redirects it to a specific point or direction. The invention can also be applied to other equipment that collects light, such as film and digital projectors.
2. Description of the Prior Art
Lighting fixtures are often used in theater, television, touring productions, and architectural applications. The lighting fixtures typically have a light source and a collection means to redirect the light to a specific point or direction. Often only a small portion of the light is redirected to the desired point or direction. Collection efficiency ranges from 20% to 60% of the light produced by the lamp. Light collection efficiency is an important issue in fixture design.
Larger lamps usually have a filament or arc that is of significant size. The large size of the light source and the lack of complete collection efficiency require that the means of collection be of significantly larger size than the lamp. A large reflector or other means of collection is required if the direction of light needs to be controlled accurately. The larger the ratio of the size of the means of collection to the size of the source, the greater the control of the accuracy of the output. This ratio is an important factor to consider when selecting the best means of collection. A smaller ratio generally allows for a more compact package, which typically leads to a lower cost. However, the smaller size ratio reduces the efficiency with which the light is collected.
A typical current art system for lighting used in the entertainment industry is illustrated in U.S. Pat. No. 5,268,613 by Cunningham, issued Dec. 7, 1993. This general method for collecting light produced by a lamp has been used by most of the major manufacturers of lighting equipment for many decades. A schematic representation of this type of collection system is shown in FIG. 1.
The system 1 for collecting light shown in FIG. 1 is capable of operating with reasonable efficiency even with a poor collection percentage. Light source 2 is shown to be of moderate size. The light rays 3 emanating from the light source propagate in all directions. Rays 4 are reflected by the reflector 5 toward the light path. A typical reflector of this type would collect approximately two-thirds of the light emanating from the source. Those light rays 6 that emanate opposite the reflector do not get collected and are wasted. The reflected rays 7 that are reflected from the reflector are directed towards the aperture 8. The light that emanates from the center of the source 2 is focused to, in the case of an elliptical reflector, a focus of the ellipse 9. FIG. 1 shows this focus point to be at the center of the aperture 8. Light that emanates from the extremities 10 of the source is reflected from the reflector at an angle significantly different than that of the center rays. This angle is related to the distance of the reflector to the source divided by the size of the source. A smaller angle generally results in improved efficiency and a more compact size of the aperture and image lens. Tracking these extremity rays in FIG. 1, one can see that the rays do not hit the focal point as the center rays do. They are reflected at a substantial angle from the center rays. This angle determines the size of the aperture. The aperture 8 may contain an object to be projected or just be a round hole. The light that passes through this aperture is refracted by the image lens 11. The image lens 11 images the object in the aperture 8 on a wall or scenic element in a typical application, such as in theatrical productions. This method of collecting light is typical of most lights used by theaters and television studios. This proportion of the source to reflector, aperture and image lens, as depicted in FIG. 1, is generally what is used today.
FIG. 2 shows the ray trace of a system 1′ that has a smaller reflector to source length. The reflector 5′ extends further forward than the reflector 5 shown in FIG. 1. The extended reflector collects more light. The problem with this design is that the size of the aperture 8′ and image lens 11 need to be much larger.
FIG. 3 shows a reflector system 1″ that has a reflector 5″ that is larger than that shown in FIG. 1. The distance between the reflector 5″ and the source 2 is also greater. This results in the collected light being more parallel. The big problem with this design is that the image lens also needs to be large. A large reflector not only makes the system larger, but a large lens creates a poorer image. A larger lens requires a more sophisticated design to create the same image quality as a smaller lens.
FIGS. 1, 2 and 3 illustrate the problems in designing a compact, low cost, and efficient collection and imagining system. An improvement of one of the parameters of the system generally results in the degradation of another.
FIG. 4 shows another type of collection system 1′″ often used in video or digital projectors. It is also used to a lesser extent in lighting fixtures. FIG. 4 depicts the same source 2 as in FIGS. 1, 2, and 3. The rear light rays 4 contact a spherical reflector 14. This light is redirected to the source and onto a condenser lens 16. The forward light rays 18 also contact the condenser lens. Upper and lower rays 6 are lost. The loss of the upper and lower rays 6 is the main disadvantage of this type of system. The light that is directed onto the condenser lens 16 is refracted to the aperture 8. The size of the aperture 8 relates to the ratio of the distance between the source 2 and lens 11 and the distance between the lens 11 and the aperture 8. Generally this type of system results in rays that are more parallel, and requires a smaller aperture. This leads to the image lens 11 also being smaller. Overall the condenser system allows for a relatively compact system, a smaller image lens, and more parallel rays. The main drawback of this type of system is poor collection efficiency.
Accordingly, it is an object of the present invention to provide a light collection system that is compact.
It is another object of the present invention to provide a light collection system that requires a small, less expensive object lens.
It is still another object of the present invention to provide a light collection system that has improved collection efficiency.